Striped spin liquid crystal ground state instability of kagome antiferromagnets

TL;DR

This paper discovers a new spin liquid state in kagome antiferromagnets that breaks certain symmetries and may explain the instability of the Dirac spin liquid, with potential relevance to real materials.

Contribution

It introduces a projected BCS state with lower energy than the Dirac spin liquid, revealing a possible instability and new ground state in kagome antiferromagnets.

Findings

Identifies a lower-energy projected BCS state with symmetry-breaking features.

Suggests this state as an instability of the Dirac spin liquid.

Links the state to observed lattice distortions in Zn-Paratacamite.

Abstract

The Dirac spin liquid ground state of the spin 1/2 Heisenberg kagome antiferromagnet has potential instabilities[1-4]. This has been suggested as the reason why it is not strongly supported in large-scale numerical calculations[5]. However, previous attempts to observe these instabilities have failed. We report on the discovery of a projected BCS state with lower energy than the projected Dirac spin liquid state which provides new insight into the stability of the ground state of the kagome antiferromagnet. The new state has three remarkable features. First, it breaks both spatial symmetry in an unusual way that may leave spinons deconfined along one direction. Second, it breaks the U(1) gauge symmetry down to $Z_2$. Third, it has the spatial symmetry of a previously proposed "monopole" suggesting that it is an instability of the Dirac spin liquid. The state described herein also shares a remarkable similarity to the distortion of the kagome lattice observed at low Zn concentrations in Zn-Paratacamite suggesting it may already be realized in these materials.